Excelitas'
infrared sensing technologies are playing a vital role in creating a healthier,
safer and cleaner tomorrow. We have gained worldwide recognition for the design
and production of our thermopile array modules.
These arrays include detectors composed of several thermocouples typically
connected in series. They are DC-type detectors and, thus, best suited for
non-contact temperature measurement. Our thermopile modules are based on silicon
micromachining technology. A special IR-absorption layer covers the hot
junctions, creating the sensor’s sensitive area.
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Thermopile linear arrays with digital interface consist of a thermopile
line/matrix array sensor with integrated ASIC, E2PROM, a microcontroller with
integrated 10-bit analog-to digital converter for signal processing and
interfacing.
The microcontroller controls the multiplexer of the thermopile line/matrix
sensor as well as all internal operations. These include measurements and
calculations for the object, ambient temperatures and post-processing of the
temperatures to output them via a digital serial interface (SMBus). The
temperature-dependant signal of the thermopile line array elements is
subsequently fed through an analog-input multiplexer into a low noise, low
offset chopper amplifier with constant gain. The amplified thermopile signal, a
voltage reference signal and the signal from the on-chip integrated PTAT
(ambient temperature) sensor is connected to an output multiplexer which
alternately feeds the signals to the analog digital converter (ADC) of the
microcontroller.
After analog-to-digital conversion, the resulting digitized voltage signals
are stored in the microcontroller’s RAM. Based on the calibration settings
stored in the TPLM’s E2PROM and on the described measurement results, ambient
temperature voltage signal (VTamb) and normalized voltage signals for individual
pixels (Pi) are calculated from the raw signals.
An SMBus-compatible, two wire bidirectional serial interface is provided to
read out the sensor’s temperature signals and for Read/Write access to the
sensor’s configuration data and calibration parameters. The SMBUS allows
connection of a master device (MD) and one or more slave devices (SD).